Electronic device



March 24, 1959 w. R. AIKEN 2,379,445

ELECTRONIC DEVICE Filed Feb. 8, 1956 4"Sheets-Sheet 1 'WIL E i 1' I J air 4, 4 E' .1.

El 311 Ii 5 x b INVENTOR ATTORNEY WILLIAM ROSS AIKEN March 24, 1959 w.R. AIKEN 2,879,446

' ELECTRONIC DEVICE Filed Feb. 8. 1956 4 Sheets-Sheet z CATHODE- RAY 48TUBE 26 VERTICAL SWEEP T. V.

VERT. SYNC. RECEIVER 46 WILLIAM ROSS AIKEN BY%M,5@

ATTORNEY INVENTOR March 24, 1959 I w. R. AIKEN 2,879,446

ELECTRONIC DEVICE Filed Feb. 8-, 1956 v 4 Sheets-Sheet 5 INVENTOR WILUAMROSS AIKEN ATTORNEY March 24, 1959 w. R. AIKEN I ELECTRONIC DEVICE! 4Shets-Sheet 4 4 Filed Feb. 8, 1956 mm mm \1.

INVENI" OR WILLIAM ROSS AIKEN N -m m r I I l ll United States PatentELECTRONIC DEVICE William Ross Aiken, Los Altos, Calif., assignor, bymesne assignments, to Kaiser Industries Corporation, a corporation ofNevada Application February :8, 1956, Serial No. 564,166

Claims. (Cl. 315-21) The present invention relates to electron dischargedevices and more particularly to thin cathode-ray tubes of the generaltype set forth in co-pending application Serial No. 355,965, filed May19, 1953, now abandoned; copending application Serial No. 504,281, filedApril 27, 1955; ,copending application Serial No. 656,874, filed May 3,1957; copending application Serial No. 703,340, filed December 12, 1957;and Patent No. 2,795,731 which issued June 11, 1957, which are capableof polychrome operation.

In the prior art, it has been proposed to display the television imagesignal by means of a cathode-ray tube using one or three electron gunsdirected at a target screen comprising discrete sensitized areas ofelectron sensitive fluorescent materials which are capable of emit tingthe desired color component elements such as red, blue, and green. Thesesensitized areas haveassumed a variety of configurations such as dots,lines, and pyramids. Various combinations have been proposed to providemeans for scanning the target screen in accordance with the scan of thetransmitted image, and for modulating, controlling .and orienting theelectron beam to produce the desired luminous color and to limit theimpingement thereof to only the desired sensitized area. The electronbeam or beams may be caused to scan the three primary color areas eitherin sequence or simultaneously so that the luminosity of the three colorvalues are additive to the human eye to thereby reproduce the hue andsaturation of the particular color signal or to produce black and whiteimage areas. Numerous systems and structures have been proposed tocontrol and modulate the electron beam so as to thereby produce thedesired scanning .of the sensitized areas and to prevent the impingementof the electron beam, or any portion thereof, upon undesired colorsensitized areas. The display arrangements proposed by the prior artinclude many relatively complicated and expensive deflecting grid andmasking arrangements which are designed to limit the impingement of theelectron beam on only the desired primary color area.

The prior art attempts to employ a masking arrangement disposedimmediately in front of and slightly spaced from the target screen havebeen confronted with the problem of picture'brightness due to theextreme current loss of the electron beam in passing through the mask.In certain instances, the current lost or absorbed by electronimpingement on the mask has been as much as eighty-seven percent of theentire beam current. In attempts to effect a picture brightness whichwould be commercially acceptable, higher voltages have been employed.High-voltages have inherent disadvantages and limits due to theirdangerous nature and an expense beyond the range which is commerciallyfeasible.

Accordingly, it is an object of'the instant invention to produce acathode-ray tube having a masking arrangement capable of permitting thepassage of only'the desired electrons of'the electron beam while at thesame time absorbinga minimum of beamcurrent.

Another object of the instant invention is to produce a cathode-ray tubecapable of exhibiting a polychrome display and utilizing a small numberof components so as to be inexpensive to manufacture and operate.

A further object is to produce a cathode-ray tube ca pable of effectingpolychromedisplays on the target screen thereof and having a relativelysmall depth dimension as compared with its length and width.

A still further object is to produce an electron discharge device havingextreme stability and color fidelity for exhibiting polychrome displays.

In accordance with one embodiment of the instant invention, thecathode-ray tube comprises a target screen having a plurality of stripsof fluorescent material capable of emitting light ofditferent primarycolors which are cyclically repeated across a surface thereof.An'electron gun is provided to deliver a beam of electrons along amarginal edge of the target. The linear set of deflection electrodes,which is used to selectively deflect the beam to a. zone adjacent thesurface of the target, is positioned in adjacently spaced relation withrespect to the marginal edgeof the target along which'the electron beamis initially delivered. A set of deflection electrodes adapted ,toselectivelydeflect the beam into reg istration with the target strips isprovided adjacent the surface of the 'targetand spaced therefromanamount sufficient to permit passage of an electron beam there between. Agrid wire assembly is disposed within .a zone intermediate thefirst-mentioned set of deflection electrodes and the region defined bythe target. .In this arrangement, the angle through which the beamis.deflected by the deflection electrodes determines the fluorescentstrip with which the beam will register.

()bjects and advantages other than thosehereinabove set forth will beapparent to thoseskilled in the art upon reading the followingdescription in connection-withthe attached drawings, in which:

Figure 1 is a front view of the cathode-ray tubejwith sections thereofpartly broken away to. moreclearly. illustrate the internal components,

Figure 2 is a sectional view of thecathode-ray tube illustrated inFigure l.taken along line ,2 2 thereof,

Figure 3 is a schematic illustration of a suitablesystern employing theinstantcathode-ray tubefor the polychrome displayof televisionvprograming, I I

Figure 4 is an enlarged side .view of a-portion of the high voltagesection of the tube to more clearly illustrate the electron beamdeflection angles of the embodiment shown in Figures 1 and 2,

Figure 5 is a side view of a modified version of the tube shown inFigures 1, 2 and 4, 3 a

Figure -6 shows another modified version of the tube wherein twoelectron beams are employed, I

Figure 7 is a front view of an embodiment of the invention,

Figure 8 is a sectional view of the cathode-ray tube shown in Figure 7taken along line 8-8, and

Figure 9 is a front view of an embodiment ofthe invention shown indiagrammatic form.

There is shown in Figures 1 and 2 an envelope .8 which is adapted tocompletely house the internal components of the instant tube andmaintainthe desired vacuum therewithin. An electron gun 10 of any of theconventional types employing, preferably, an integral electrostaticdeflection system, such as that described in an article entitled,Improved Electron Gun for 'Cathode-Ray Tubes, by L. E. .Swedlund inElectronics for March 1946, is disposed within the envelope 8. Theelectron gun 10 is adapted to deliver an electron'beam 12. A lineararray of horizontal deflection electrodes 14 is disposed within theenvelope '8' along the upper marginal edge thereof. Each of theelectrodes 14 is.

Patented Mar. 24, 1959 provided with an electrical conductor 16 which isadapted to pass through the wall of the envelope 8 and the entire groupof conductors may be assembled and positioned within suitable cablemeans 18 and in turn connected, to a horizontal sweep generator 54, asclearly illustrated in connection with Figure 3.

A slotted accelerating electrode 20 is disposed in spaced andsubstantially parallel relation with respect to the entire array ofdeflection electrodes 14. The electrode 20 is suitably energized througha conductor 22 adapted to electrically couple the electrode 20 to asuitable power supply within a television receiver 46, as clearlyillustrated in Figure 3. The aforementioned group of components may bereferred to as the primary section of the tube.

Disposed beneath and extending substantially the entire length of theprimary section, there is a pair of focusing and accelerating electrodes24 provided with a suitable electrical conductor 26 which is adapted topass through the wall ofsth'e envelope 8 to a power supply within thetelevision receiver 46, asclearly shown in Figure 3. It is to beunderstood that, in certain appllcations, it may be desirable to employan additional pair of focusing and accelerating electrodes similar tothe pair of electrodes 24. In such event, these additional electrodescould be-disposed beneath and slightly spaced from the electrodes 24 andconnected to the same power supply employed to energize the electrodes24 or to a separate power supply to operate at potential different fromthat of electrodes 24. The electrodes 24 and any additional similarelectrodes which maybe desired may be referred to as the transitionsection of the tube.

The high voltage or secondary section of the tube comprises anelectrically conductive transparent panel 34 having a coating thereon ofa material which when struck by impinging electrons will become excitedand fluoresce an amount in proportion to the energy of the mpinging beamof the electrons. The fluorescent coatmg or target screen is comprisedof alternate strips 38 and 40 of fluorescent material cyclicallyrepeated across one entire surface of the panel 34. Thestrips 38 are ofa fluorescent material, such as zinc phosphate, manganese activated [Zn(PO :Mn], which will emit red light when excited by an impinging beam ofelectrons and the strips 40 are of a fluorescent material, such as zincsulfide, silver activated (ZnSzAg), which will emit blue light whenexcited by impinging electrons. It has been found advisable to make eachstrip 38 and 40 of a width of approximately thirty (30) mils.Accordingly, if four hundred eighty-seven strips (243 /2 of the strips38 and 243% of the strips 40) are employed, the resultant display areawill have a vertical dimension of fifteen inches.

It will be noted that the electrically conductive panel 34 is providedwith a conducting wire 36 which is adapted to be electrically connectedto a source of potential which is positive with respect to the potentialof the electron beam 12. The potential is obtained from the power supplywithin the television receiver 46, shown in Figure 3.

Opposite and spaced from the phosphor coating com prised of the strips38 and 40, there is a plurality of deflection electrodes 28. Each of theelectrodes 28 is provided with an electrical conductor 30 adapted topass through the tube envelope 8 to a vertical sweep generator 56, asshown in Figure 3. The various conductors 30 may be cabled togetheroutside of the tube envelope 8 within a cable 32.

In certain applications of the instant tube, it may be deemed necessaryto view the display presented on the target screen from two sides. Insuch event, the vertical Tdeflection electrodes 28 are formed of atransparent conducting material such as, treated with stannic'chloride(SnCl for example, glass i 4 t 4 Within the zone defined bythe targetscreen and the vertical deflection electrodes 28, there is disposed agrid wire assembly comprised of a plurality of grid wires 42 having acommon conductor 44 leading to a power supply within the televisionreceiver 46, as illustrated in Figure 3. The number of grid wires 42 isonly one-half that of the number of strips of fluorescent materialatfixed to the panel 34; or, in other-words, there are as manyindividual grid wires 42 in the grid wire assem; bly as there are strips38of red light emitting phosphors. The grid wire assembly is disposediinsuch a manner relative to the phosphor strips 38 and 40 that a singlewire 42 is directly opposite and spaced from each of the strips. 38which emitsred light. The diameter of each of the grid wires 42' is ofthe order of thirty (30) mils; therefore, the diameter of the wires 42is substantially equal to the width of each of the phosphor strips 38and 40.

Figure 3 illustrates a system employing the instant cathode-ray tube inconnection with the reception of a television display in color. Astandard RCA color receiver circuit may be employed such as, forexample, RCA Model CTIOO, Chassis No. CTC2. For purposes ofsimplification, the above referred to receiver is shown in diagrammaticform by reference numeral 46. The color TV receiver 46 includes a powersupply capable of energizing the various components of the instant tubeas will be hereinafter be set forth in'detail.

The horizontal and vertical sweep sync signals are fed to a syncamplifier 48 through their respective coupling conductors 50 and 52. Thesync amplifier 48 amplifies the horizontal and vertical sync signalswhich are then fed to the horizontal and vertical sweep generators 54and 56 through electrical conductors 58 and 60, respectively.The'horizontal sweep generator 54 is coupled to the horizontaldeflection electrodes 14 through the conductors 16 which are housedwithin the cable 18. The vertical sweep generator 56 is coupled to thevertical deflection electrodes 28 through the conductors 30 which arehoused within the cable 32.

The grid wires 42 are coupled to the power supply within the receiver 46by the conductor 44.

The video signals carrying the information to be displayed by theinstant tube are fed from the receiver 46 to a video amplifier 62through a suitable electrical conductor 64 for conducting the red colorcontrol signals and an electrical conductor 66 for conducting the bluecolor control signals. The video amplifier 62 amplifies the red and theblue signals and they are then fed through conductors 68 and 70,respectively, to a color gating circuit, diagrammatically shown andgenerally indicated by reference numeral 72. The gating circuit 72 isoperative to selectively feed the signals carrying the appropriate colorinformation to the electron gun 10 through an electrical conductor 74.

In the operation of the instant invention, the electron gun 10, uponsuitable energization by an incoming video signal (television use),causes an electron beam 12 to be delivered along a path which is insubstantially parallel alignment with the longitudinal axis of thelinear array of horizontal deflection electrodes 14. Initially, all thehorizontal deflection electrodes 14 are maintained at some potentialpositive with respect to the cathode potential of the electron gun 10and negative with respect to the potential of the slotted acceleratorelectrode 20. As the electron beam 12 enters the region of electrostaticfield established by the first horizontal deflection electrode 14 mostadjacent to the source of the electrons, the repelling force of saidfield causes the beam 12 to be deflected downwardly in a direction awayfrom said electrode. The

equal potential lines established within the horizontal deflectionelectrodes 14 deflect the electrons through the: open side oftheelectrodes 14 toward and through the slot formed in the slottedelectrode 20 and hence into the transition and high voltage sections ofthe tube.

In obtaining a display, .the horizontal deflection electrode's114are,asmentione'd above, initially maintained at their maximum negative valuewith respect to the slotted accelerator electrode 20, and thenselectively driven in a positive direction toward said potential value.This displaymay also be achieved in the opposite manner; 'in otherwords, all the horizontal deflection electrodes 14 may be initiallymaintained in their fully charged state and then discharged or driventoward a negative potential value. Whichever method is used, thefrequency of change (from negative to positive or charged to discharged)is controlled by the horizontal sweep generator 54.

It was found that satisfactory results were obtained by initiallyimpressing on the horizontal deflection electrodes 14 a potential of 400volts positive with respect to the cathode potential of the electron gun10. The slotted electrode 20 is maintained at 800 volts potentialpositive with respect to the cathode potential of the electron gun 10. I

In achieving a line scan, energizing signals are applied to thehorizontal deflection electrodes 14, preferably in a successiveoverlapping manner. That is, a signal is applied to the deflectionelectrode closest to the source of electrons, which drives thatelectrode in a positive direction approaching the value of the potentialon the slotted electrode 20. However, prior to the instant the potentialvalue on the first electrode reaches a value substantially equal to thepotential of the slotted electrode 20 (800 volt positive potential), apositivegoing signal is applied to the next adjacent deflectionelectrode 14. Obviously, when the potential on the first of theseelectrodes reaches the approximate value of the potential on the slottedelectrode 20, a field-free zone is established within the region definedby the slotted electrode 20 and the horizontal deflection electrode 14,thereby permitting the electron beam 12 to travel unaffected to the nextadjacent horizontal deflection electrode 14. This procedure is repeatedalong the entire array of electrode 14 in such a manner that the chargeon 'at least two of the electrodes is always changing at the same time.

The electron beam 12 after being deflected, accelerated and focused inthe primary and transition sections, is caused totravel along a path inclose proximity to the vertical deflection electrodes 28. The verticaldeflection system is operated in much the same manner in which thehorizontal deflection system is operated. The signals applied to thevertical deflection electrodes 28 are preferably applied in overlappingmanner so that the potential value on at least two adjacent electrodes28 is changing at the same time. Initially, the vertical deflectionelectrodes 28, the grid wires 42, and the fluorescent target comprisedof the phosphor strips 38 and 40 are maintained in the order of 16 kv.potential positive with respect to the cathode potential of the electrongun 10. By virtue of thefact that each of the elements of this portionof the high voltage section is maintained at an equal potential value, afield-free region is established therewithin permitting the electronbeam 12 to travel unobstructively within the field-free region until asuitable negative potential with respect to the potential of the targetstrips 38 and' 40 is applied to one or more of the vertical deflectionelectrodes 28.

As' one electrode 28 is driven negative with respect to the cathodepotential of the target, it exerts a deflecting force on the beam 12,causing it to be deflected toward the fluorescent target through thegrid wire assembly 42. The impingement of the electrons upon the propercolor strip of the target, as hereinafter described, causes it to giveoff luminescence of an intensity which is directly proportional to theintensity of the impinging electron beam 12.

In order to obtain a full polychrome display, the surface of the panel34 opposite the surface coated with the target strips of phosphor 38 and40 may be coated with 5 a phosphor of the type which emits green lightupon the impingement of an electron beam. For instance, such a phosphoras zinc orthosilicate manganese activated (Zn SiO :Mn)v may be used. Insuch an embodiment, an additional electron gun modulated by the signalcarrying the information to be displayed in green is positioned adjacentthat other surface of panel 34 and is deflected by another set ofvertical deflection electrodes. In the alternative, the target strips 38and 40 may be separated by a phosphor strip of green light emittingphosphor. Beam switching means would then be employed to cause theelectron beam to selectively sweep the desired fluorescent material uponreceipt of the corresponding color informa:

tion sothat the device would be operated with but a single electron gunmodulated by the red, blue, and green signals.

In order to present an image in color, the individual pictures whichhave been sent from the transmitter in each of the primary colors mustbe reassembled at the receiver. In order to simplify the followingdiscussion, we will assume that the first of the three color embodiments described above is used so that the green primary color is producedby a separate electron gun upon a separate target, whereas the red andblue signals are reproduced by the modulation of a single electron gunacting upon a target having strips of alternate red and blue phosphors.In such an embodiment, the color picture may be produced by afield-sequential method. In such a method, the electron beam is firstcaused to scan the entire face of the target screen in a manner wherebyonly the phosphor strips 38 emitting red light are struck and therebyexcited by the beam, forming a red raster.

During the next succeeding scanning operation, the beam will be causedto impinge only on those phosphorstrips 40 which emit blue light,thereby forming a blue raster,

Acting under the control of the transmitted signal, the beam 12 changesin intensity and thereby causes the spot of light emitted by the excitedphosphor to eifect a .corresponding change in brightness as it movesalong each strip and thus recreates the light and shadows of theoriginal scene. Since the light spot on the target screen moves inprecise step with the scanning process of the television camera at thetransmitting station, each dot of light falls in its proper place andhas its proper value of light or shade. at the receiver is accomplishedso rapidly--a single primary color being emitted during each period ofthe beam sweep of the individual strips of phosphor-that these stripsare not perceived separately one after the other, but appear to theviewer as a blend of colors existing simultaneously.

In the alternative, a polychrome display may be produced by aline-sequential method. In this method and in somewhat similar fashionto that used in the conventional black and white television picturetube, the per.- sistence of the eye to retention of light images isutilized to reduce the flicker of transmission. Alternate lines arefirst scanned and then the picture is retraced on the remaining lines,so that the entire picture is covered twice during the one-thirtieth ofa second raster. In this system, the lines are scanned so that aftereach line of red, there is a scan of a line of blue and then of a lineof red and a line of blue, alternatively, and when the bot torn line isreached, the electron beam retraces the face of the target, utilizingthe remaining color strips. Simultaneously, of course, the green targetis scanned and, since only two of the three primary colors areinterlaced,

the crawling which is experienced in the line interlaceorline-sequential system is inherently reduced to such a degree that itis unnoticed, as in conventional black and.

white TV receivers.

Atthis point in the description of the invention, the.

exact nature and function of the grid wire assembly must be explained.As briefly pointed out in a precedingsection of the description inconnection with the disposition of the individual wires 42 with respectto the individual Obviously, the reassembling process snails caldeflection electrodes 28. The manner in which the grid wires 42 operateis best illustrated in connection with Figure 4 which shows the electronbeam 12, shown in full line, deflected so as to impinge on only thephosphor strips 38 which give ofl red light. When the electron beam 12is deflected so as to pass through theopening between adjacent gridwires 42, it impingeson the phosphor strips 40, as shown in Figure 4 inbroken lines.

It will be understood that the angle through which the beam is'bent bythe force applied by the deflection electrodes 28 determines whether thebeam will impinge on the phosphor strip 38 or 40.

As mentioned above, the point of beam registration on the target screenis determined by the angle through which the beam is caused to bendunder the influence of the deflecting force established by the verticaldeflection electrodes 28. In the instant embodiment of the invention, itis necessary to cause the beam 12 to bend through one angle in order toimpinge upon the strips 38 to achieve a red raster, and to bend throughanother angle to impinge upon the strips 40 to achieve a blue raster. Itwill be readily apparent that if theenergizing signals impressed on thevertical deflection electrodes 28 are maintained within the same range,the energy or velocity of the electron beam 12 as it travels in the highvoltage section must be of a constant energy in order to bend and passthrough the space between adjacent grid wires 42 and impinge on thephosphor strips 38. The beam 12 must rapidly then assume another energyto be deflected by the deflection electrodes 28 through the spacebetween adjacent grid wires 42 and impinge on the phosphor strips 40.

' It should be noted here that the angle of the deflected beam isdependent upon the ratio of the energy of the beam to the deflectingforces acting upon it. In order to obtain the desired color change, itis only necessary to change this ratio in any convenient manner. Forinstance, the deflecting forces acting upon the beam in both the primaryand the secondary section of the beam may be kept constant and theenergy of the beam varied independently, as by raising the voltage ofthe transition section. A beam with a higher energy component will bedeflected through a lesser angle than that of a smaller energy componentwhen acted upon by the same deflecting force. For another example, thedesired result may be had by changing the energy of the beam in thesecondary section by increasing the voltage on both the verticaldeflection electrodes 28 and upon the targets 38 and 40. The beam isaligned on one of the two colors by utilizing a voltage of, for example,kv. upon the target plate and a potential of +1 kv. on the deflectionelectrodes 28. Then, for the other color, the target is run at +11 kv.and the deflection electrodes at +2 kv. In this example, no over-allchange is made in the voltage drop between the target and the deflectingelectrodes so that, therefore, the deflecting force remains constant at9 kv. but, however, the energy of the beam in the secondary section issufliciently varied by the 1 kv. change so that it is deflected througha different angle and therefore registers upon a different color. Inanother example, the opposite technique is used and the deflectionforces are changed rather than the energy of the beam, for any specificcolor selection. In another instance, the energy of the beam is variedby modulating the cathode potential. As previously explained, the higherenergy beam is deflected less by a given deflection field than a lowerenergy beam.

In yet another example, the overlapping action of the deflection platesis increased for one color and decreasedfor another. By increasing ordecreasing the area of field overlap in the deflection system, thedeflection angle of the beam is changed by the changing action of thedeflecting electrodes. .It should be explained at this point that if thedot sequential method is used in forming the color picture, then thechange from one color to the other must be effected very rapidly,whereas if the line sequential method is used, then the change need notbe quite so rapid and, of course, if the field sequential method isused, then the color change need only be made once for each completeraster field.

In addition, as shown in Figure 5, the position of the electron beam inthe secondary section may be shifted to achieve different colorregistrations. The electron beam is deflected, focused, and acceleratedin the primary and transition sections by horizontal deflection plates14, slotted accelerator 20, and focusing and accelerating electrodes 24.The side portions of each pair of electrodes 24A-Bare normally operatedat one potential positive with respect to the potential ofthe cathode ofthe electron gun 10, for example +5 kv. Similarly, both sides of thepair of electrodes 24C and 24D are operated at the same potential, inthis example +3 kv., with respect to the potential of said cathode.After passing through the transition section, the electron beam is thenin the secondary section and is ready to be deflected by verticaldeflection electrodes 28. As shown in Figure 5, if the potential on 24Bis made slightly more negative, say of the order of 200 volts, from thaton 24A, the electron beam will be caused to pass closer to the surfaceof electrode 24A than to the surface of electrode 24B. Correspondingly,if the potential on accelerating and focusing electrode 24C is similarlymade more negative with respect to the potential of the electron beamthan the potential of electrode24D, the electron beam will be caused tostraighten its path and pass close to but not impinge on electrode 24C.As is shown in Figure 5, this gives a shifted path to the electron beamas its passes through the transition section and serves to pass theelectron beam closer to the grid wire assembly 42. Accordingly, .whenthe electron beam is deflected by one of the electrodes 28, if it iscloser to the grid wire assembly 42 it will 'not be acted upon with asmuch force and, correspondingly,

will be deflected through a smaller angle. than the electron beampassing normally between the transition section which will be deflectedthrough alarger angle and impinge upon the color strip adjacent to thatimpinged on by the electron beam whose path was shifted. By switchingthe potentials on electrodes 24B and 24C to correspond to the colormodulation of the signal, the electron beam will be caused to fall uponthe red phosphor strips and the blue phosphor strips, alternatively andin the proper order.

The target screen may be coated or deposited with a film of aluminum bythe well-known process of aluminizing to absorb any secondary electronswhich may be emitted from the phosphor material of the strips 38 and 40.Also, any secondary electrons emitted from the grid wires 42 in adirection toward the target screen wil l also be absorbed by this filmof aluminum.

The double-bend deflection of the electron beam, as set forth above,reduces beam blow-up" and thereby provides powerful inherent focusingability. Specifically, the beam is not brought down to a small spotuntil the second deflection force is applied to the beam (the forceapplied by the vertical deflection electrodes 28 Due to the very natureof the double-bend deflection system, it is possible and relativelysimple to etfect focus of the electron beam in the horizontal dimensionseparately from focus in the vertical dimension. Accordingly, and in theshadow mask device described herein, it may be advantageous to useastigmatic focusing ofthe electron beam to overcome any problems ofmisregistration due 9 to. sl ippage of the pattern .or raster. Forinstance, if a slight: slippage occurred which would cause .amisregistration of the electron beam in relation to the shadow mask, itis possible that a thin beamof the ordinary size would create a black orblank spot on the phosphor target. Since either of these results wouldbe noticeably :objectionable, it would be well to astigmatically focusthe beam so that it is narrow in its horizontal dimension but longin itsvertical dimension. A beam of this type will give sharp definiton butwill also simultaneously impinge upon both of the limiting grid wiresofthe shadow mask to insure that a good portion of -the beam passesthrough the grid wires in the proper fashion, regardless of any minormisregistration of the electron beam upon the shadow mask. While someloss of brilliance occurs, due to the fact that a certain portion of theelectron beam is masked by the grid wires and does not pass through toexcite the phosphor screen, this is compatible with the situation in theconventional color tubes wherein asubstantial portion of the electronbeam is always lost at the color mask. However, this type of cathode-raytube has the advantage over the conventional cathode-ray tube in thatthe beam current can be increased to make up for any electron losses. Inany case, the amount of astigmatic focusing will, of course, depend uponthe seriousness of the misregistration problem.

In certain applications of the instant cathode-ray tube, it may bedeemed advisable to maintain the grid wires 42 at substantially the samevoltage as the voltage impressed on the vertical deflection electrodes28 at their maximum charged value, while thetarget screen is maintainedat some voltage value positive with respect thereto. For example, onemay employ a corresponding maximum value of +10 kv. for the verticaldeflection electrodes 28, a substantially equal potential on the gridwires 42, and a potential of the order of kv. on

- the target strips 38 and 40. Inasmuch as the electrodes 28 and'thegrid wires 42 areof substantially the same voltage value, there will beno potential gradient between them, thereby establishing a field-freezone within which the electron beam 12 may travel unaffected untildeflected.

By maintaining the above 'set forth voltage values on the respectivecomponents, the electron beam 12, after passing through the spacebetweenthe adjacent grid wires 42, will be accelerated toward therelatively positive target area and be very sharply focused on thephosphor target strips 38 and 40. This focusing, which is sometimescalled, post-deflection focusing, is the result of the acceleration'ofithe' electron beam in the area between the grid wires" and thetarget and can readily be shown by-a :vector :analysis. In other words,if the beam has any cross sectional'area at all, this area will bedecreased since the outer edges of the beam will be turnedinwardly-towardrits: center. The advantages of this postdeflectionfocusing are,=of course, obvious, since a beam with greater-energy isconcentrated at a smaller point of impaction the target to give greaterbrilliance'and definition than otherwise.

-Figure '6 illustrates another method of achieving color selection:byemploying two electron beams 12 and 12a of .the same energyiandvelocity. It will be noted that'the electron beam -12 is caused totravel within the high voltage or secondary section of the tube along apath which .is closed to the vertical deflection electrodes 28 than .theelectron beam 12a. As-described above, the angle-through which the beamis deflected determines the color selection. In the instant'embodiment,the deflecting .force established by the deflection electrodes 28acts toa ditferenhdegree on .each of the beams 12 and 12a. The beam 12,.whichis closer :to the array of vertical deflection electrodes 28, isdeflected througha larger angle than :theQbeam 12a. This result.is:achieved due to the fact that the force imparted on the beam 12 isconsiderably' -greater than the force imparted on the beam 12a.

Accordingly, it will be noted that the beam 12 is deflected through anangle causing the'beam to bend and travel through the space betweenadjacent grid wires 42 toward the phosphorstrips '38, while the beam 12ais caused to be deflected through a smaller angle and travel through thespace between adjacent grid wires 42 toward the phosphor strips 40.

Another modification of the cathode-ray tube is shown diagrammaticallyin connection with Figures 7 and 8. It will be noted that the modifiedversion employs a grid wire assembly between the transition section andthe high voltage section of the tube. Its function is similar to that ofthe grid wire assembly shown and described in the embodiment shown inFigures 1 and 2, being in the nature of a mask which acts to permit thepassage therethrough of only those electrons which have been deflectedthrough a predetermined angle, while all others impinge on the surfaceof one or more of the individual wires of the assembly. Further, it willbe noted that the target screen iscomprised of vertically disposedstrips of fluorescent material which are parallel to one another andextend across the entire surface thereof.

There is shown in Figures 7 and 8, an electron gun adapted to deliver anelectron beam 82 in spaced and parallel relation with respect to theupper marginal edge of a target screen. Said target screen is comprisedof a conducting glass panel 94, one surface of which is provided with aplurality of vertically disposed phosphor strips 96 and 98. A lineararray of horizontal deflection electrodes 84 is disposed along andspaced from the upper marginal edge of the target screen so as to applydeflecting forces to the beam '82 upon suitable energization. in spacedcoextensive relation with respect to the linear array of deflectionelectrodes 84, enabling the electron beam 82 to pass therebetween. Thelinear array of horizontal deflection electrodes 84 and the slottedaccelerating electrode 86 comprise the so-called primary section of thetube which is substantially identical with the corresponding section ofthe embodiment shown and described in connection with Figures land 2.,

The transition section of the tube comprises two pairs of acceleratingand focusing electrodes 83 and 9t). These electrodes are disposed incoextensive and spaced relation with respect to the slottedacceleratingelectrode 86.

Disposed beneath the pair ofelectrodes 90, there is a grid wire or maskassembly comprising a plurality of grid wires 92 which are disposed inparallel relation with respect to one another. r

An electrically conductiveglass panel 94 having a plurality of strips 96and,98 of fluorescent material cyclically repeated across a surfacethereof, is disposed beneath the assembly of grid wires 92. The strings96 are composed of a phosphor such as zinc phosphate, mangaueseactivated, which is capable of emitting red light when excited by animpinging beam of electrons. The strips'98 are composed of a phosphorsuch as zinc sulfide, silver activated, which is capable of emittingblue light when excited 'by an impinging beam of electrons. The strips96 and 98 are formed in a width of approximatelythirty (30) mils.

A set of vertical deflection electrodes 100 is disposed in adjacentlyspaced relation with respect to the surface of 'the lpanel 94 which isprovided with the fluorescent strips 96 and 98. In certain applicationsof the cathoderay tube, it may be desirable to view the displaypresented on the target screen from two diametrically opposed directionsand, in such event, the deflection electrodes 100 may be formed of anelectrically conductive transparent material such as, for example,glass. The aforementioned combination of elements, including thepanel'94 having'the fluorescent strips 96 and 98 and the set ofdeflection electrodes 100, comprise the so-called secondary or highvoltage section of the tube.

It must be understood that the modification shown in A slottedaccelerating electrode 86 is disposed 11 Figures 7 and 8 is merelydiagrammatic and that for purposes of simplicity, the electricallyconductive wires for the respective electrodes of the tube are notshown. The glass envelope enclosing the entire assembly which isnecessary to provide a vacuum environment is likewise not shown.

In operation, initially, all the horizontal deflection electrodes 84 aremaintained at a potential of approximately 400 volts positive withrespect to the cathode potential of the electron gun 80. The slottedaccelerating electrode 86 is maintained throughout the entire operationof the tube at substantially 800 volts potential positive with respectto the electron gun 80. Accordingly, the electron beam 82 delivered bythe electron gun 80 is initially de fiected by the electric fieldestablished by the deflection electrode 84 closest to the gun. Thedeflected beam 82 is caused to travel downwardly through the slot formedin the slotted accelerating electrode 86 and is then successivelyfocused and accelerated by the accelerating and focusing electrodes 88and 90. The pair of electrodes 88 may be satisfactorily maintained at +2kv. potential positive with respect to the cathode potential of theelcctron gun 80, and the pair of electrodes 90 may be maintained atsubstantially +8 kv. potential positive with respect to said cathodepotential.

Due to the fact that the electron beam 82 has a velocity component in adirection away from the electron gun 80, it may approach the assembly ofgrid wires 92 at an angle of less than ninety degrees.

Color selection is achieved by the grid wires 92 much in the same manneras color selection is achieved by the grid wires 42 of the embodimentshown in connection with Figures 1 and 2. Accordingly, the specificstrip of fluorescent material of the target screen on which the beam 82registers is determined by the angle of incidence of the beam with theassembly of grid wires 92. It will be noted that if the beam 82 arrivesat the grid wire assembly at one angle, only certain of the electrons ofthe beam are permitted to pass through the space between the adjacentwires 92, while the other electrons are blocked. On the other hand,ifthe beam is deflected through a larger angle, thereby having a largerangle of incidence, only certain of the electrons of the beam 82 will bepermitted to pass through the space between the same adjacent wires 92,While other electrons of the beam will be effectively blocked.Obviously, it will be seen that in the first instance, the beam 92 willeffectively impinge on the phosphor strip 96 which will emit red light,while in the second case, the beam 82 will impinge on the phosphor strip98 which will emit blue light.

In this embodiment, the assembly of grid wires 92 is maintained withinthe range of from fourteen (14) to sixteen (16) kv. potential positivewith respect to the cathode potential of the electron gun 80. The highvoltage section, including the target panel 94 and the verticaldeflection electrodes 100, are maintained initially at substantiallysixteen (16) kv. potential positive with respect to the cathodepotential. Accordingly, it will be readily understood that if thepotential impressed on the grid wires 92 is substantially the same asthe potential of the high voltage section, there will be no supplementalfocusing effected on the electron beam between the grid wires and thehigh voltage section. But, if the potential impressed on the grid wires92 is lower than that of the high voltage section, additional focusingwill be effected.

As the electron beam 82 enters the high voltage section of the tube, itwill travel unaffected downwardly through the field-free zone defined byand established between the target screen and the vertical deflectionelectrodes 100, until one of the electrodes 100 is caused to be driventoward zero potential. Upon being so driven,

that deflection electrode will establish a relatively negative electricfield, thereby imparting a force to the electro'nbeam causing ittobend'toward and'impinge on the target panel. The particular phosphorstrip impinged by the beam is determined"by the angle of incidence withthe assembly of grid wires92 or, in otherwords, the angle through whichthebeam is bent by thedefiecting. forces established by the horizontaldeflection electrodes 84 of the primary section of the tube.

' The horizontal and vertical deflection electrodes 84 and 100,respectively, are energized by, suitable sweep generators in a mannersubstantially identical to that described in connection with theprevious embodiment.

The angle through which the electron beam 82 is bent within the primarysection of the tube is determined by the relative energy or velocity ofthe electron beam 82 and the forces exerted thereon by the electricfield established by the horizontal deflection electrodes 84. It

is deemed advisable to maintain the forces of the electricfield'substantially constant and to vary the energy or velocity of theelectron beam 82 by modulating the cathode of the electron gun 80. Inaccordance therewith;- upon the receipt by the gun of the red -informa--tion containing signal, the cathode is energized to lower the energy orvelocity of the emergent beam so as to be deflected by the horizontaldeflection electrodesthrough an angle to pass through the grid wireassembly in registration with the phosphor strips96. Accordingly, uponthe receipt of the blue information, the cathode is so modulated as toraise or increase the velocity of the emergent beam. The increasedenergy or velocity beam will bedefiected through a smaller angle by thedeflection electrodes 84 so as to travel in the high voltage section inregistration with thepho sphor strips 98.

'The preceding description has been directed to the use-of phosphorstrips of only two of the primary colors. red: and blue; however, itmust be understood that other combinations of phosphors could likewisebe employed. Certain combinations may include the employment of stripsoffluorescent material capable of emitting red and green light or in otherapplications it may be desirable to employ fluorescent strips with red,blue, and green light emitting characteristics.

In the embodiment'shown in Figure 9, the electron beam is passed througha drift tube section before passing into the field-free region of theprimary section.

Theprinciple of drift tube acceleration is well-known inresultaccomplished in the embodiment described in Figures 7 and 8 bymodulating the cathode of the electron gun. The electron beam emanatesfrom electron gun and before reaching the primary section and theregionbetween the horizontal deflection electrodes 84 and the slottedaccelerating electrodes 86, passes through a drift tube device comprisedof the two pairs of plates 111 and the oscillating pair of plates 112.The two pairs of plates 111 are connected to the power supply of theunit and are maintained at l-kv. potential positive with respect to thecathode potential of the electron gun 80. The pair of plates 112 areconnected to an RF oscillator 113 which, in turn, is controlled by thecolor information signal. Thus, the voltage on the drift tube isincreased and decreased responsive to the color signals and therebyimparts to those electrons passing, through the tube an increase ordecrease in energy."

Thus, as the electron beam leaves the drift tube apparatus, it will havea definite energy level dependent upon the voltage characteristics ofthe pair of plates 1 12. By operating the oscillator 113 to imparteither a high or low voltage to the pair of plates 112, the electronbeam may be divided into bunches of electrons of two In the embodimentdiagrammatically shown in different energy levels.

v13 Thus, as the -:electron beam is deflected in the primary section bythe electrodes 84, his deflected at two distinct angles resultant fromthe two different and distinct energy levels of the electron beam.Accordingly, the angle through which the electron beam is deflected isdistinctly different upon thereceipt of blue information than upon thereceipt of red information and, therefore, the proper registration withthe phosphor strips 96 and 98 is accomplished.

It will be obvious to those skilled in the art that a drift tubeapparatus may be placed in an embodiment such as that shown in Figures 3and 4 in the area just before the secondary section. Accordingly, theelectron beam will be imparted with two diflerentand distinct energylevels prior to the time that it is deflected in the secondary section.Thus, if the oscillation of the drift tube device is co-ordinated withthe color signal information, the beam will be properly deflected toimpinge upon the corresponding phosphor color strip. Insuch case, thedrift tube would have a long andvflatconfiguration rather than the shortand round configuration described in Figure 9. 7

Other combinations of the invention will be obvious to those skilled inthe art to provide other embodiments of a-polychrome electron dischargedisplay device operated in accordance with the invention set forthhereinabove.

I claim:

, '1. A cathode-ray tube having a target comprising a plurality ofstrips of fluorescent material arranged in a predetermined pattern,means for delivering a beam of electrons along 'a path substantiallyparallel to said target, means for modulating the velocity of theelectrons in said beam of electrons prior to its delivery alongsaidpath, means for selectively deflecting said beam from differentintervals on said path into registration with correspondingly differentintervals on said target, and masking means for discriminatelypermittingregistration with predetermined different target stripsresponsive to variations in the velocity-of the electrons in said beamof electrons.

2. An electron space discharge device having& target provided with aplurality of strips offluorescent material,

an electron beam source for delivering a beam along a path in adjacent,substantially parallel relation with the marginal edge of said target,means for imparting discrete velocities to said electron beam as itpasses along said path, means for selectively deflecting the beam fromdifferent intervals on said path into a zone adjacent said target,masking means comprising a plurality of grids disposed in parallel andadjacent relation with said strips of fluorescent material to maskcertain of said strips from said beam as delivered toward said maskingmeans at a first predetermined angle of incidence relative thereto, andto mask other predetermined ones of said strips from said beam asdelivered at a second predetermined angle of incidence relative thereto,and means for deflecting the beam from said zone toward said maskingmeans at said first and second predetermined angles of incidence toeffect registration thereof with said other of said certain strips insaid respective deliveries.

3. A cathode-ray tube for reproducing polychromatic images comprising anelectron sensitive target having a plurality of fluorescent stripscapable of emitting light of the primary colors arranged in apredetermined pattern, an electron beam source means for delivering abeam along a path adjacent and substantially parallel to a marginal edgeof said target, means for selectively applying deflecting forces to saidbeam causing it to be deflected to a zone in spaced and parallelrelation with said target, masking means comprising a grid wire assemblyin adjacent spaced relation with respect to said target to presentcertain predetermined areas to said beam and to mask other predeterminedareas from said beam as delivered at a predetermined angle of incidencerelative 14 to said maskingmeans, andmeans fortselectively apply ingdeflecting forces to said beam to cause same to be bent in the directionof said grid wire assembly at said predetermined angle of incidence.

4. A cathode-ray tube as defined in claim 3 wherein said grid wireassembly comprises a plurality of parallel .and electrically conductiveelements disposed in coextensive relation with respect to alternate onesof said strips to mask said alternate strips from said beam responsiveto direction of the beam toward said mask at said predetermined angle ofincidence, and to mask the other strips from said beam responsive todirection of the beam .toward said mask at a second angle of incidence,and means for adjusting the angle of incidence of the beam relative tosaid mask.

5. A cathode-ray tube for reproducing polychromatic images comprising anelectron sensitive target having a plurality of fluorescent stripscapable of emitting light of at least two of the primary colors arrangedin a predetermined pattern, an electron beam source means for deliveringa beam along paths substantially parallel to a surface of said targetand to a zoneadjacent and parallel to a surface of said target, maskingmeans including a grid wire assembly disposed in adjacently spaced andparallel relation with respect to said target to mask certainpredetermined strips from said beam as delivered toward said maskingmeans at a first predetermined angleof incidence relative thereto and tomask different ones of said strips from said beam responsive to deliveryof the beam in the direction thereof at a second given angle ofincidence, and means for'selectively applying deflecting forces to saidbeam causing it to be directed in the direction of said grid wireassembly at said first and second angles of incidence and intoimpingement with said different 'and said certain ones of said strips insaid respective deliveries on said target.

6. Acathode-ray tube for reproducing polychromatic images comprisingan'electron sensitive target having a plurality of fluorescent stripscapable of emitting light of the primary colors arranged inapredetermined pattern, an electron beam source means for delivering abeam along a path adjacent and substantially parallel to a marginal edgeof said-target, means for selectively applying deflecting forcesto saidbeam causing it to be deflected to a zone in spaced and parallelrelation withsaid target, maskingmeans disposed between said path andsaid target for selectively discriminating electron impingement on saidtarget whereby only electrons deflected through a predetermined anglemay pass through said masking means and into registration withpredetermined ones of said strips, and means for selectively applyingdeflecting forces to said beam causing it to travel through said maskingmeans into registration with said predetermined strips.

7. A method of presenting a polychromatic display on an electronsensitive target comprising the steps of delivering a beam along amarginal edge of said target, applying deflecting forces to said beamcausing it to be directed to a zone parallel to and spaced from asurface of said target, maintaining said zone free from spuriouselectric fields, applying deflecting forces to said beam causing it tobe deflected in a direction toward said target, and effectivelydiscriminating the flow of electrons by masking steps prior to theirimpingement on said target.

8. A cathode-ray tube comprising a target wherein at least one surfacethereof is coated with a plurality of strips of electron sensitivematerial arranged in a recurrent pattern across said surface, anelectron beam source means for delivering a beam of electrons along amarginal edge of said target, means for applying deflecting forces tosaid beam causing it to be deflected to a zone adjacent to and spacedfrom said target, means for applying deflecting forces to said beamcausing it to be deflected toward and into impingement with said target,

nd masking meajns cei i p risiqg 5a grfidi :wire: assembly fleet. s;minatin p s es. .sa throng whereln 91215 the; eieietiio'ns :dfi saic lbeamdefl eeted thrw ceitagin predetermined: angles gwiili jass itlifigsaiqlimiaskinggzneans nt edeterm a :s'ai dg been :tie i be dieflecitejdthrongh said: angie and into, egistraiion with :predetezniined: fies id;strigs i d i rsi es in :difi: vials 13f sa'id beamio defiect same: inioregist iauwiih:

h said'target- 2,633,547 La'w' L 'Mar/31,1953" 12. In a cathode ray tubeas set forth in claim 11 in 2,689,269 Bradley 4---. Sept. 14, 1954 whichsaid means for delivering a beam of electrons to 2,692,532 Lawrence Oct.26, 1954 the zone adjacent said target includes an electron gun2,728,024 Ramberg Dec. 20, 1955 having a cathode element, and said meansfor modulating 45 2,795,731 Aiken June 11, 1957 the velocity of saidbeam includes means for coupling

